The seals most widely used in fluid power devices can be categorized into two groups; the energized seal including the U-seal, V-seal, lip seal, etc. which are energized either by fluid pressure or by a mechanical spring, and the solid section ring such as the O-ring, Quad-ring, D-ring, Rectangular-rings, etc. In applications where the seal provides a sliding pressure barrier such as shaft seals, piston seals, etc., the energized seal is being used without any exception. The energized seal is an annular seal made of a resilient material having a cross section of U- or V-shape and installed in a groove disposed on an outside or inside circular cylindrical surface in such a way that the concave side of the cross section faces the high pressure side and the convex side faces the low pressure side. The pressure-energized seals are called U-rings, V-rings or lip ring seals depending on the shape of the cross section and are made of a resilient and elastic material such as rubber or other elastomers. The fluid pressure contained at the concave side of the cross section of a pressure-energized seal spreads out the lips or the free-extremities of the cross section of the seal and establishes a leak-proof slidable contact between the lips of the seal and the solid surfaces confining the seal in its groove. The spring-energized seal is essentially a pressure-energized seal comprising an additional means for spreading out the lips of the seal, which means may be a ring of a mechanical coil spring, a metalic ring of U-shaped cross section or a hollow O-ring that is fitted within the U or V shaped groove of the seal facing the high pressure side. Without any exception, all of the energized seals employed in today's fluid control devices are "one-way" seals that provide a leak-proof pressure barrier in one direction only, which is from the concave side to the convex side of the seal cross-section. Consequently, two seals have to be installed back to back in tandem in all applications which require "two-way" seals such as hydraulic or pneumatic actuator cylinders. Another shortcoming possessed by the conventional energized seals such as the U-ring, V-ring and other lip seals is their poor performance at a high temperature as well as at a low temperature. Usually, the energized seals are made of materials with high thermal expansion coefficient. As the operating temperature deviates significantly from the ideal design condition, the seal expands or shrinks to a much greater extent than the metalic element constituting the boundaries confining the seal. As a consequence, the lips of the energized seal may be crushed partially because of the dimensional incompatibility between the seal and the seal-groove and partially because of the structural instability arising from the asymmetric cross section of the U-shaped or V-shaped cross section of the energized seals.